Delaware

1-13011

76-0526487

(State or other jurisdiction

(Commission

(IRS Employer

of incorporation)

File Number)

Identification No.)

675 Bering Drive, Suite 400
Houston, Texas

77057

(Address of principal executive offices)

(Zip Code)

Quality People. Building Solutions. As of May 18, 2011

Safe Harbor Statement This presentation contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These statements are based on the current plans and expectations of future events of Comfort Systems USA, Inc. and involve risks and uncertainties that could cause actual future activities and results of operations to be materially different from those set forth in the forward-looking statements. Important factors that could cause actual results to differ include, among others, the use of incorrect estimates for bidding a fixed-price contract, undertaking contractual commitments that exceed our labor resources, failing to perform contractual obligations efficiently enough to maintain profitability, national or regional weakness in construction activity and economic conditions, financial difficulties affecting projects, vendors, customers, or subcontractors, our backlog failing to translate into actual revenue or profits, difficulty in obtaining or increased costs associated with bonding and insurance, impairment to goodwill, errors in our percentage-of-completion method of accounting, the result of competition in our markets, our decentralized management structure, shortages of labor and specialty building materials, retention of key management, seasonal fluctuations in the demand for HVAC systems, the imposition of past and future liability from environmental, safety, and health regulations including the inherent risk associated with self-insurance, adverse litigation results and other risks detailed in our reports filed with the Securities and Exchange Commission. A further list and description of these risks, uncertainties and other factors are discussed under "Item 1A. Company Risk Factors in the Company’s Annual Report on Form 10-K for the year ended December 31, 2010." These forward-looking statements speak only as of the date of this filing. Comfort Systems USA, Inc. expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statement contained herein to reflect any change in our expectations with regard thereto or any change in events, developments, conditions or circumstances on which any such statement is based. 1

Vision To be the nation’s premier HVAC and mechanical systems installation and services provider. 2

Mission 3 To provide the best value HVAC and mechanical systems installation and service, principally in the mid-market commercial, industrial, and institutional sectors, while caring for our customers, employees and the environment and realizing superior returns for our stockholders.

4 Values Act with honesty and integrity. Show respect for all stakeholders. Exceed customer expectations. Seek “win-win” solutions. Demonstrate spirit, drive, and teamwork. Pursue innovation. Achieve premier safety performance. Commit to energy efficiency. Communicate openly.....and often. Impact our communities positively.

Comfort Systems USA’s TEAM 5 Bill Murdy – Chairman/CEO Experience Industry: 20 years CSUSA: 10 years Military: 10 years Bill George – EVP & CFO Experience Industry: 13 years CSUSA: 13 years Legal: 6 years Brian Lane – President & COO Experience Industry: 26 years CSUSA: 7 years Tom Tanner – SVP-Region 1 Experience Industry: 34 years CSUSA: 12 years Dean Tillison – SVP-Region 2 Experience Industry: 37 years CSUSA: 13 years Chuck Diltz – SVP-Region 3 Experience Industry: 26 years CSUSA: 7 years Brewster Earle – VP-Energy Services Experience Industry: 29 years CSUSA: 8 years Jeff Coleman – President-National Accounts Experience Industry: 26 years CSUSA: 2 years

6 Comfort Systems USA National Commercial, Industrial, Institutional HVAC/Piping/Plumbing/Energy Efficiency Strong balance sheet 47% new construction; 53% service, repair, retrofit 2010 Full Year Revenues $1.1 billion 2011 Run Rate $1.2 billion

Comfort Today 7

8 Our Companies

What We Do Commercial, Industrial, Institutional HVAC – A $40B+ Industry Drivers Building comfort – a “necessity” Mechanical equipment – requires service, repair, replacement Increasing technical content and building automation Energy efficiency and Indoor Air Quality (IAQ) emerging Outsourcing 9 Commercial HVAC Applied Systems Energy Efficiency Piping

Industry Trend Toward Service & Replacement (Recurring Revenue) 5.3 million commercial buildings Recurring service 20-year replacement cycle / retrofits for energy efficiency “Inventory” of future business OEMs note significant deferred maintenance and replacement over recent years 10 Source: The Trane Company

11 Revenues by Activity 2010 – Full Year 2011 - Year To Date New Construction/Installation Replacement Service & Maintenance

12 Diverse Project Mix Average Project Size: $435,000 Value of Projects >$1M: $1,085.9 M Average Project Length: 6-9 months Value of Projects <$1M: $782.8 M (As of March 31, 2011) Total Projects = 4,299

Diverse End-Use Base Distribution: 1% Religious and Not-for-Profit: 1% Residential: 1% Lodging and Entertainment: 2% Other: 9% Retail/Restaurants: 8% Multi-Family: 4% Office Building: 10% Manufacturing: 12% Top 20 Customers Served by 16 different Comfort operating units Largest customer represents less than 2% of revenues 13 Healthcare: 17% Education: 19% Government: 16% As of March 31, 2011 YTD

Diverse End-Use Base 14 Omni Orlando Resort at ChampionsGate Orlando, Florida University Hospital Little Rock, Arkansas Arboretum Elementary School Waunakee, Wisconsin Iowa Renewal Energy Washington, Iowa

Competitive Advantages High-quality operations Ability to leverage and proliferate technical expertise Ability to collaborate on large jobs and share labor Energy efficiency services National multi-location service capability Purchasing economics Balance sheet strength Bonding and insurance Strong safety record 15

16 OSHA Recordable Rate Source: Bureau of Labor Statistics, Standard Industry Classification (SIC) Code 20 1710 – Specialty Trades Contractors – HVAC and Plumbing & North American Industry Classification System (NAICS) Code 23822 Safety 43% Difference 20% Difference Industry Average (October 2009 – latest available data) Comfort Systems USA (March 2011 data) Our safety record is no accident. Lost Time Injury Rate <60% of industry average OSHA Incident Rate <43% of industry average Training 97% completed 0.0 5.0 10.0 15.0 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

17 Key Financial Data – Income Statement ($ Thousands, except per share information) (Unaudited) 2011 2010 Revenues 282,059 $ 236,475 $ Cost of Services 247,850 196,967 Gross Profit 34,209 39,508 Selling, General and Administrative Expenses 42,622 37,409 Gain on Sale of Assets (85) (5) Operating Income (Loss) (8,328) $ 2,104 $ -3.0% 0.9% Net Income (Loss) from Continuing Operations (5,170) $ 1,165 $ -1.8% 0.5% Diluted Earnings (Loss) per Share from Continuing Operations (0.14) $ 0.03 $ Adjusted EBITDA (1) (3,594) $ 5,735 $ -1.3% 2.4% (1) See Slide 34 for GAAP Reconciliation to Adjusted EBITDA Three Months Ended March 31,

18 Key Financial Data – Balance Sheet ($ Thousands) 3/31/2011 12/31/2010 Cash 63,636 $ 86,346 $ Working Capital 126,668 $ 134,738 $ Goodwill 149,090 $ 147,818 $ Identifiable Intangible Assets, Net 39,088 $ 39,616 $ Total Debt 29,936 $ 29,936 $ Equity 307,067 $ 312,784 $ 

19 Revenues Note: Excludes all divested and discontinued operations

20 Operating Margins(a) (a) This table includes non-GAAP financial information because the information provided excludes goodwill impairment charges of $33.9 million for 2005 and $5.7 million for 2010. No goodwill impairment charge was recorded for 2006, 2007, 2008 or 2009.

21 Backlog (in millions) Note: Excludes all divested and discontinued operations

Profile for Growth 22 Time Earnings Incremental Service Growth Current Operations (Construction and Service) Energy Efficiency Acquisitions Service Commercial HVAC

Operations Increase Productivity Education Leadership Project Managers Superintendents Service Sales Service Operations Craft Safety Best Practices Project Management Estimating Cooperation with suppliers Prefabrication New materials and methods 23

Job Loop We review projects and apply what we have learned to improve our performance. 24 Post-Project Review Project Estimating Project Pricing Project Qualification Project Management

25 The only things that evolve by themselves in an organization are disorder, friction and malperformance. Peter Drucker

Service Increase Service* Grow maintenance base Education Employees and Customers Higher margin opportunity Recurring revenue National accounts $2.50+ of repair and replacement for every $1.00 of maintenance Target retrofit projects Energy Efficiency Indoor Air Quality (IAQ) 26 * Maintenance, service, repair, retrofit

27 National Account Customers *Trademarks and logos are the property of their respective owners.

Energy Efficiency – Retrofitting HVAC Green is Part of Our Business Energy costs drive need for efficiency. HVAC accounts for 30% - 50% of electricity usage. Energy Star (Department of Energy/EPA) / LEED (USGBC) 2 - 4 year pay outs depending on electric rates, usage, age, incentives. 28 Use Our Energy to Save Yours! ™

Growth Internal More of what we do best Service Energy efficiency Step-Out Growth New locations for existing companies Techs “on their own” Targeted acquisitions Best HVAC-oriented mechanical in new area 29

The Ideal Acquisition Candidate $20M+ in revenue Construction and service In a growing market in new area Company that has performed well in the past and has continuing demonstrable upside Organizational structure capable of sustaining/improving the company Ownership/management that wants to stay on to operate the company 30

Target Markets Boise, ID Charleston, SC Columbia/Florence, SC Dallas/Fort Worth, TX El Paso, TX Ft. Lauderdale, FL Greensboro, NC Jackson, MI Los Angeles, CA Omaha, NE Portland, OR San Antonio, TX Savannah, GA Spartanburg/Greenville, SC Tampa, FL 31 (Listed Alphabetically)

Outlook Long-Term $40B+ fragmented industry HVAC a basic necessity Commercial construction continuing Growing installed base for recurring maintenance, service, repair and retrofit Scale opportunities – service, purchasing, prefab, bonding, best practices Diverse customer base and geography Energy efficiency and Indoor Air Quality Financially and operationally sound – continuing to grow organically and by acquisition 32

What We Do 33

34 Appendix I – GAAP Reconciliation To Adjusted EBITDA (in thousands) (Unaudited) March 31, 2011 2010 Net Income (Loss) (5,170) $ 1,927 $ Discontinued Operation - (762) Income Taxes (3,699) 730 Other (Income) Expense, net 80 (12) Interest Expense, net 461 221 Gain on Sale of Assets (85) (5) Depreciation and Amortization 4,819 3,636 Adjusted EBITDA (3,594) $ 5,735 $ Note 1: We define adjusted earnings before interest, taxes, depreciation and amortization (“Adjusted EBITDA”) as net income (loss), excluding discontinued operation, income taxes, other (income) expense, net, interest expense, net, gain on sale of assets, and depreciation and amortization. Other companies may define Adjusted EBITDA differently. Adjusted EBITDA is presented because it is a financial measure that is frequently requested by third parties. However, Adjusted EBITDA is not considered under generally accepted accounting principles as a primary measure of an entity’s financial results, and accordingly, Adjusted EBITDA should not be considered an alternative to operating income (loss), net income (loss), or cash flows as determined under generally accepted accounting principles and as reported us. Three Months Ended

Contact 35 Bill George Executive Vice President and CFO 1-800-723-8431 bill.george@comfortsystemsusa.com www.comfortsystemsusa.com